Having just skimmed the Dragon Age RPG Quickstart Guide PDF for practically the first time, I've found the game's Stunts system - which gives you a chance to accomplish some interesting, useful trick if you roll an especially successful attack - rather interesting.
Is there a similar mechanism (that would extend or replace the default critical hits system) published - preferably officially - for D&D3.x?
If so, where is it available?
Pathfinder adds quite a large variety of feats that let you modify your critical hits in exactly this manner, usually causing status effects (stunning, fatigued, and so forth) or invoke a spell-like effect as part of the critical. They're all conveniently listed under Critical Feats in the Pathfinder reference site, and can easily be adapted back into D&D3.5.
3.5 itself also has a couple of similar feats, but only as Epic feats (see Devastating Critical, which just outright kills).
If you want to replace your existing crit rules without requiring specific feats for it, you can perhaps take the list of feats in Pathfinder as inspiration for possible effects and either make table for it, or let characters choose which crit they're aiming for in advance. To avoid making it overpowered, perhaps use these effect instead of the extra damage inflicted.
